Keyboards in most prior art calculators include an array of switches for entering information into the calculator. In order to conserve the number of connections necessary between the keyboard and the calculator circuitry, the key switches are arranged in an X-Y matrix and the rows and columns of this matrix are electronically scanned to detect and identify a depressed key. In many calculators using this method the keyboard scanning goes on continuously except for a short interruption while a key is still depressed after it has been detected and identified. This allows the calculator to be constantly ready for the input of new information but it also consumes extra battery power to have the keyboard scanner circuitry operating at the same time other portions of the calculator circuitry, such as the central processor, are operating.
In the preferred embodiment of the present invention, a keyboard is provided for an interactive wristwatch calculator and the key switches are arranged in an X-Y matrix. The rows and columns of this matrix are scanned in order to detect and identify a switch closure but the scanning is inhibited during the time the calculator circuitry is active. When the calculator circuitry has finished with the procedure, such as entering a number or making a calculation, the circuitry goes into an inactive mode at a significantly reduced level of power consumption and only then is the keyboard scanned.